The present invention relates to a recuperative heat exchanger, and more especially to a recuperative heat exchanger made of a ceramic material and having a plurality of flow channels which are arranged in a row adjacent to each other and which are directed parallel with respect to each other. The heat exchanger includes inlet and outlet orifices for media in heat exchange relationship. Adjacent flow channels have a common partition wall, with different media engaged in the exchange of heat flowing through adjacent flow channels, and the flow channels are offset alternatingly with respect to each other in the direction of the inlet orifice. The present invention also relates to a process for manufacturing such recuperative heat exchangers.
Recuperative heat exchangers of this type are especially suitable for gas turbines, in which case ceramic materials, such as silicon carbide SiC, silicon nitride Si.sub.3 N.sub.4 and cordierite, are used. Such a heat exchanger has already been proposed in DE-OS No. 27 07 290; it comprises a U-shaped medium conduit. Furthermore, in DE-OS No. 24 53 961 there is described a recuperative heat exchanger, especially for gas turbines, having preferably cross-shaped or Z-shaped medium conduits made of metal or ceramics. Similarly, a tubular plate heat exchanger with L-shaped medium conduits made of metal is known from U.S. Pat. No. 2,430,270. The latter heat exchanger is used particularly for heating of air or liquids, wherein hot combustion gases are used as the heating medium. The heat exchanger is of simple design and is readily disassembled for cleaning purposes. However, such a heat exchanger is not suitable for high temperature applications.
Especially in the automotive industry, heat exchangers capable of resisting gas temperatures of approximately 1300.degree. C. are needed for the development of economical vehicle gas turbine engines. For this reason, only ceramic materials come under consideration as heat exchange materials for this use. Furthermore, the problems attendant this use could not be solved entirely with regenerator heat exchangers with their rotating ceramic disks, so that resort is now being made to the recuperator type. Heat exchangers suitable for this or other applications should have a high degree of efficiency, small dimensions and a light weight. It is required furthermore that such ceramic recuperative heat exchangers operate reliably and that they may be manufactured inexpensively.